proximo

UK: /ˈprɒksɪməʊ/ US: (prok′sə mō′)

WordReference Random House Unabridged Dictionary of American English © 2025

prox•i•mo  (prok′sə mō′), adv. 

1. in, of, or during the next month:
   on the 10th proximo.
   Cf. instant (def. 11), ultimo. 

• Latin proximō ablative of proximus next. See proximal
• 1850–55

Collins Concise English Dictionary © HarperCollins Publishers::

proximo / ˈprɒksɪməʊ/ adverb

1. (esp abbreviated in formal correspondence) in or during the next or coming month: a letter of the seventh proximo
   Abbreviation: prox
   Compare: instant, ultimo

Etymology: 19th Century: from Latin: in or on the next, from proximus next